Kinetics of Cu6Sn5 and Cu3Sn intermetallic compounds growth and isothermal solidification during Cu-Sn transient liquid phase sintering process

The kinetics of Cu-Sn intermetallic compounds (IMCs) growth relates to the materials preparation, process regulation and reliability prediction in the new energy field and electronic packaging industry. As a typical instance that Cu-Sn IMCs are involved with, this work investigated the kinetics of Cu-Sn IMCs growth and isothermal solidification of Cu-Sn transient liquid phase sintering (TLPS) process for high temperature resistant packaging of the third-generation semiconductors power devices. A three-dimensional kinetics model of Cu/Sn solid/liquid interfacial reaction and the corresponding kinetics equations of Cu6Sn5 and Cu3Sn growth was established. Based on Cu-Sn IMCs growth kinetics, a parameter ξSn called the residual rate of Sn was defined to characterize the isothermal solidification kinetics of Cu-Sn TLPS process. By measuring the volume fraction of Cu and Sn, the quality fraction of residual Cu and Sn and produced Cu-Sn IMCs were determined, and thus the kinetics of Cu-Sn IMCs growth and the isothermal solidification of Cu-Sn TLPS process were experimentally studied to validate the theoretical model. The results showed that the theoretical results predicted by the model were well-matched with experimental results. Besides rising temperature, the kinetics of Cu-Sn IMCs growth and the isothermal solidification can be remarkably accelerated by decreasing Cu particle size. Reducing Sn content does not affect the kinetics of Cu-Sn IMCs growth but helps to shorten the isothermal solidification time of Cu-Sn TLPS process.